1. Significance of melanin-related metabolites as biochemical markers of melanoma(1) Normal values of 5-S-cysteinyldopa(5-S-CD) and 6-hydroxy-5-methoxyindole-2-carboxylic acid(6H5MI2C) in serum and urine were obtained from 33 healthy Japanese. The urinary excretion of both markers showed significant decrease in elderly subjects as compared with middle-aged subjects, while the serum concentration showed no age-dependent differences.(2) Values of those 4 markers in melanoma patients have regularly been followed. Among the 4 markers serum 5-S-CD appears to reflect most sensitively the progression of melanoma.Some patients showed pathological values of serum 5-S-CD(above 10 nmol/L) prior to the detection by image diagnosis. On the other hand, 6H5MI2C in serum and urine was found to be of little clinical significance.(3) Serum 5-S-CD values have been analyzed every month in 2 years' period in 10 healthy subjects. No values exceeded 10 nmol/L, the upper limit of normal value, in the 240 samples.2. Improvement of HPLC determination of serum 5-S-CD The previous method for the HPLC determination of serum 5-S-CD required 80 min for each chromatographic run. Pre-treatment of serum samples has been improved to reduce the time for each analysis to 40 min, which enabled to double the analytical capacity.